No-Regret measure proof gate - read-only dossier-safe status

Builds a deterministic advisory proof gate for No-Regret measure claims. It covers measure identity, target domain, scenario coverage, budget anchor, cost and benefit ranges, regulatory fit, decision owner, objection window, evidence source, next management gate and due date. The endpoint is read-only and does not approve investment, reserve budget, book finance, create workflows/HITL items, call external connectors or mutate billing, settlement, tariff or device-control state.